Some observations on washout of brown trout (Salmo trutta L.) eggs in Teesdale streams

Brown trout (Salmo trutta) in Teesdale lay their eggs in the streambed gravels in the Autumn, here the eggs slowly develop to emerge as young fry in the Spring. Whilst the eggs are in the gravel they are vulnerable to displacement by high water velocities. Eggs removed in this way are not thought to remain viable since they are very susceptible to death through physical shock - especially in the earlier stages of development. Streams in Teesdale are known to be amongst the most flashy in England and thus are good sites in which to study egg washout. Three field sites were used for the study of egg washout in Teesdale - Great Eggleshope, Thorsgill and Carl becks. This report describes preliminary studies of a varied nature into this subject from which an attempt is made to assess the importance of egg washout to the survival of brown trout in Teesdale.